Blowdown Process Research Articles

Revealing the impact of sample enrichment method on concentration and cytotoxicity of volatile disinfection byproducts in drinking water: A quantitative study for liquid-liquid extraction

Liquid-liquid extraction (LLE) combined with the N2 blow-down method is a promising tool for bioanalysis of drinking water. However, detailed information on which disinfection byproduct (DBP) classes are retained in LLE extracts is currently unavailable. In this study, the recovery of seven classes of volatile DBPs and total adsorbable organic halogens (TOX) during the LLE method, combined with three common N2 blow-down methods, for bioanalysis in real tap water was analyzed at a 2-L scale, along with their corresponding cytotoxicity. The total concentration of seven classes of volatile DBPs in drinking water in Suzhou ranged from 64.6 to 83.0 µg/L, with the majority contributed by trihalomethanes (THMs: 59.9 µg/L), haloaldehydes (HALs: 5.4 µg/L), haloacetamides (HAMs: 3.4 µg/L), and haloacetonitriles (HANs: 3.2 µg/L). During the LLE - N2 blow-down process for bioanalysis, about 69–85 % of targeted volatile DBPs and 64–75 % of TOX were lost, respectively. Seven classes of volatile DBPs accounted for 52.8–64.3 % and 23.8–61.3 % of TOX in tap water and LLE - N2 blow-down samples, respectively, suggesting that targeted aliphatic DBPs are the key contributors to TOX. Furthermore, although LLE - solvent exchange had a better recovery performance than other N2 blow-down methods, the recoveries of volatile DBPs using this method were still not ideal. For example, HALs and HAMs had a slightly better recovery (>50 %), while most volatile DBPs had a poor recovery, including iodo-trihalomethanes (I-THMs, 0 %), haloketones (28 %), THMs (26 %), halonitromethanes (33 %), and HANs (38 %). During LLE - solvent exchange, 31 % and 36 % of targeted DBPs and TOX, respectively, in real tap water can be retained, which shows better performance than non-ionic macroporous copolymers (XAD). More importantly, the water volume required in this method for cytotoxicity analysis is 2 L, which greatly reduces the burden of water sample collection, transport, and pre-treatment compared to XAD (which typically requires 5 or 10 L). In general, this paper reveals the fate of volatile DBPs during LLE - N2 blow-down and indicates that LLE - solvent exchange is a good substitute for the XAD method in bioanalysis.

Nitrogen Experiments on a Supersonic Linear Cascade For ORC Applications

A novel experiment has been conceived at Politecnico di Milano for the study of the flow within and downstream of supersonic cascades of Organic Rankine Cycle (ORC) turbines. This paper documents the first phase of the research, focused on the preliminary tests and studies performed by operating the facility with nitrogen as working fluid, to demonstrate the technical relevance of the experiment and the validity of the measurement system in a simplified thermodynamic condition. The set of measured data includes, beside the inlet total thermodynamic state, eight static pressure values obtained via taps manufactured on the test section rear end-wall, both within the bladed and semi-bladed region of the cascade, as well as a total pressure probe to retrieve the cascade performance. A double-passage Schlieren equipment was also employed to visualize the density gradients. Experiments show an outstanding repeatability, indicate a quasi-steady cascade operation during the blow-down process for all the pressure signal considered, and demonstrate a remarkable periodicity among two consecutive channels also in off-design conditions. Experimental data were also compared with CFD simulations, resulting in an excellent agreement for the pressure data acquired both within and downstream of the cascade.

Engineering Pore Environments of Sulfate-Pillared Metal-Organic Framework for Efficient C2 H2 /CO2 Separation with Record Selectivity.

Engineering pore environments exhibit great potential in improving gas adsorption and separation performances but require specific means for acetylene/carbon dioxide (C2 H2 /CO2 ) separation due to their identical dynamic diameters and similar properties. Herein, a novel sulfate-pillared MOF adsorbent (SOFOUR-TEPE-Zn) using 1,1,2,2-tetra(pyridin-4-yl) ethene (TEPE) ligand with dense electronegative pore surfaces is reported. Compared to the prototype SOFOUR-1-Zn, SOFOUR-TEPE-Zn exhibits a higher C2 H2 uptake (89.1 cm3 g-1 ), meanwhile the CO2 uptake reduces to 14.1 cm3 g-1 , only 17.4% of that on SOFOUR-1-Zn (81.0 cm3 g-1 ). The high affinity toward C2 H2 than CO2 is demonstrated by the benchmark C2 H2 /CO2 selectivity (16 833). Furthermore, dynamic breakthrough experiments confirm its application feasibility and good cyclability at various flow rates. During the desorption cycle, 60.1 cm3 g-1 C2 H2 of 99.5% purity or 33.2 cm3 g-1 C2 H2 of 99.99% purity can be recovered by stepped purging and mild heating. The simulated pressure swing adsorption processes reveal that 75.5 cm3 g-1 C2 H2 of 99.5+% purity with a high gas recovery of 99.82% can be produced in a counter-current blowdown process. Modeling studies disclose four favorable adsorption sites and dense packing for C2 H2 .

Numerical simulation of gas-liquid interface in high-pressure water-blowing chamber

The load on the water chamber increases with the pressure level and blowing rate of the system, and the demand for theoretical and experimental studies related to the quantitative parameters of water chamber blowing safety becomes more and more frequent. In this paper, CFD computational fluid dynamics method is used to carry out the dynamics modeling and simulation of three-dimensional non-constant gas-liquid two-phase internal flow field of the test water chamber and the actual water chamber blowdown process to obtain the dynamic distribution of flow parameters in the water chamber under different working conditions. The results found that to ensure the safety of the water tank, as long as to ensure that the high-pressure air into the water tank at the end of the first two stages, the “bubble” movement process always does not interfere with the bulkhead, you can ensure that the high-pressure air in the water tank in the free expansion and gravity floating state, the water tank pressure will be only slightly higher than “gas - water cross-section” of the static pressure, at this moment the water chamber safety.

Numerical investigation of the depressurization performance in blowdown pipe using method of characteristics

The coolant leaks quickly after the break of the high-pressure pipeline system. The rapid pressure decrease and fluctuation will further affect the integrity of the pressure boundary and the effective heat removal of the reactor core in the early phase of blowdown. Generally, numerical simulation plays a vital role in the safety analysis of nuclear power plants (NPPs) under severe accidents like loss of coolant accident (LOCA) conditions. In this paper, one-dimensional two-phase hydrodynamic equations and essential closure models are established to describe the internal pipe flow firstly. Then, method of characteristics (MOC) realized by a self-programming code is introduced, which is different from the numerical scheme of system analysis code RELAP5 in the simplification and discretization. Finally, combined with the Edwards blowdown experiments, the two numerical solution methods are compared on modeling, sensitivity analysis, and calculation results under various working conditions. The influence of back pressure variation on the solution of thermal–hydraulic parameters has been considered during the blowdown process. The solution result of RELAP5 is highly related to the set discharge coefficients, which are usually given according to experience. However, the solution result of MOC can be enveloped by that of RELAP5 with different discharge coefficients. In addition, the results solved by MOC are closer and more conservative to the experimental values during the early phase of blowdown with low void fraction fluid. It lays a foundation for the further calculation and safety analysis of the complex loop system under LCOA conditions.

Experimental visualization and characteristics of bubble nucleation during rapid decompression of supercritical and subcooled carbon dioxide

The rapid decompression of sub-cooled and supercritical carbon dioxide was investigated experimentally using schlieren and regular high-speed photography. An optically accessible expansion tube was designed and constructed. A test campaign with initial pressures ranging from 6.45–9.02 MPa and initial temperatures from 297–308 K was performed. High-speed schlieren imagery was used to visualize the decompression waves, evaporation waves, and an oscillatory phase change region present in the blowdown process. The time history of pressures at different locations along the expansion tube were recorded using fast response pressure transducers. Image and pressure signal analyses were performed to extract decompression wave speeds and evaporation wave speeds. Results were compared to analytical models and other experiments reported in the literature. The relationship between pressure undershoot and wave speed to the initial conditions was analysed.

Study on estimation of break diameter in the small break loss of coolant accident based on NSGA-II

The break diameter estimation in the small break loss of coolant accident (SBLOCA) is an important work in the field of nuclear safety. It can help the operators to judge the severity of the SBLOCA in time and play an important role in reducing the damage caused by the accident. In this study, a break diameter estimation model for the blowdown process of the SBLOCA is built based on the NSGA-II and the blowdown model of the pressurizer in the SBLOCA. The model uses monitoring data such as liquid level, temperature and pressure of the pressurizer during the blowdown process to calculate the break diameter in the SBLOCA. It can be analyzed from the results that the break diameter estimation model can estimate the break diameters accurately and quickly in the SBLOCA, the errors between the calculating results of the break diameter estimation model and the actual results are no more than 18.9%, and the calculation time of the model is less than 310 s. When the calculation process reaches the maximum generation of the model, the values of fitness functions in the model approaches the minimum values.

21 Bar Yoshimin Boiler Maintenance with Controlling Residual Phosphate

Boiler as the steam generator is usually utilized as a turbine drive and other industrial processes. Boiler needs good treatment and surveillance to keep its best performance. Boiler water (BW) and boiler feed water (BFW) quality control is essential in boiler maintenance since it preserves boiler from crust, corrosion, and carry over, moreover, it also prevents boiler pipe to break. Boiler maintenance in sugar refinery factory is carried out by controlling the quality of BFW, Chemical injection (inner maintenance) and blowdown of boiler water. BFW mineral content (SiO 2 , total hardness) is maintained as small as possible using a softener (cation resin) or demineralization unit (cation and anion resin). Chemical injection is performed by the addition of soda in order to control the pH of boiler water. Phosphate addition aims to tie up total hardness level which is caused by concentration process of water boiler and slipped of hard water from BFW. Blowdown process has purpose to reduce crust and corrosion caused by mineral concentrate inside boiler. The experiment was conducted by controlling pH of BFW from 7.5-8.5, maximum total hardness at 3 ppm, maximum SiO 2 concentration at 3 ppm and maximum Total Dissolve Solid (TDS) at 100 ppm while BW was controlled its pH at 10.5-11, maximum total hardness at 20 ppm, maximum SiO 2 concentration at 50 ppm, maximum Total Dissolve Solid (TDS) at 2000 ppm, and residual phosphate ion between 4 – 10 ppm. The experiment time was adjusted as a milled day or about for 140 days. The result of the experiment showed that the treatment had a good impact on the condition of the boiler drum pipe.

Study on the thermal hydraulic characteristics of a simulated pressurizer during the blowdown process

The small break loss of coolant accident (SBLOCA) is a typical accident studied by many researchers. However, blowdown characteristics of the SBLOCA have not received sufficient attention. In this study, an experimental system for simulating the inherent characteristics of a pressurizer during the blowdown process is built under a low-pressure condition, and a mathematical model for predicting the thermal–hydraulic characteristics during this blowdown process is established. The simulation results are compared with experimental results to verify the accuracy of the mathematical model; the simulation and experimental results were in good agreement. The effects of different nozzle diameters and different initial pressures on the thermal–hydraulic characteristics are analyzed according to these simulation and experimental results. The results show that the steam temperature and pressure in the heating container have a high decline rate during the early stage of the blowdown process, and the decline rate subsequently decreases and remains steady, while the water temperature during the blowdown process decreases steadily. During the blowdown process, the nozzle diameter and initial pressure have little effect on the steam temperature, water temperature, and pressure, but the decline rates of both the liquid level and mass flow exhibit an increasing trend as the nozzle diameter and initial pressure increase. Compared to the water temperature, steam temperature, and container pressure, the liquid level and mass flow are more appropriate parameters for predicting the characteristic parameters of the blowdown process.

Blow-down calibration of a large ultrasonic flow meter

Oil and gas production industries use large (diameter > 0.8 m) ultrasonic flow meters (USMs) to measure exhaust gas from flare stacks, emissions from smokestacks, flow of natural gas, etc. Since most flow laboratories do not have compressors with sufficient flow capacity (>10 kg/s) to calibrate large flow meters, calibrations are performed using the blow-down method where flow is generated by discharging high pressure tanks, leading to significant flow transients. We used an array of critical flow venturis (CFVs) in a blow-down facility to calibrate a large (D = 89.5 cm) 8-path ultrasonic flow meter. The flow transients associated with the blow-down process caused large spatial and temporal variations in temperature that dominated (40%–67%) the uncertainty budget. Our uncertainty analysis accounts for transient-generated uncertainties and provides guidelines for improving blow-down calibrations of large flow meters.

An Experimental and Numerical Analysis on the Dynamical Behavior of a Safety Valve in the Case of Two-phase Non-flashing Flow

Pressure Relief Valves (PRVs) are key elements of any hydraulic system in the process industry, especially in chemical plants or hydraulic power transmission systems. Their task is to maintain the system pressure beneath a prescribed maximum pressure and vent the excessive fluid in an emergency scenario. This paper addresses the static and dynamic behavior of a Direct Spring-Operated PRV of conical shape in the presence of two-phase non-flashing flow, that is, water-air mixture. First, experimental results on the force and discharge characteristics of such a valve in a wide range of the air-to-water mass fraction are presented. Our test facility includes a custom-designed PRV with 42.5 mm inlet pipe diameter, an inlet pressure up to 6.6 bar(g) and a maximum lift of 10 mm. Additionally, the empirical results on the static characteristics, notably fluid force on the valve disc and discharge coefficients are reported as a function of the liquid mass fraction and valve lift. In the second part of the paper, we present the development of a Matlab-based simulation tool that is capable of predicting the dynamics and stability of such a valve in the case of two-phase, non-flashing, frozen-mixture flow. Moreover, the effect of system parameters, such as spring stiffness and reservoir capacity are recorded. Finally, we also present results on the stability of the opening and closing the multi-phase flow influence on the stability of the blowdown process.

High-Speed Schlieren and Particle Image Velocimetry of the Exhaust Flow of a Pulse Detonation Combustor

The exhaust flow of a pulse detonation combustor (PDC) is investigated for different operating conditions. The PDC consists of two units: the deflagration to detonation transition section, and the exhaust tube with a straight nozzle. High-speed high-resolution schlieren images visualize the shock dynamics downstream of the nozzle. The flow dynamics during one full PDC cycle is examined via high-speed particle image velocimetry. A well-suited solid tracer particle for supersonic reactive flow is determined in a preliminary study to minimize the PIV measurement error. The investigated operating conditions of the PDC differ in fill fraction, which is the percentage of the tube filled with a reactive mixture. With increasing fill fraction, the flow features grow in size and strength as the propagation velocity of the leading shock increases. The blowdown process of the PDC is characterized by several exhaust and suction phases. An increase in the fill fraction results in a stronger first exhaust phase, whereas the subsequent suction and exhaust phases remain almost unaffected.

A relative entropy for expanders of the harmonic map flow

In this article, we focus on the uniqueness question for (expanding) solutions of the harmonic map flow coming out of smooth 0-homogeneous maps with values into a closed Riemannian manifold. We introduce a relative entropy for two purposes. On the one hand, we prove the existence of two expanding solutions associated to any suitable solution coming out of a 0-homogeneous map by a blow-up and a blow-down process. On the other hand, generic uniqueness of expanding solutions coming out of the same 0-homogeneous map of 0 relative entropy is proved.

Optical Measurement of Fluid Motion in Semi-Valveless Pulse Detonation Combustor with High-Frequency Operation

ABSTRACTThe purge layer of a semi-valveless pulse detonation cycle (PDC) needs to be minimized for operating at a gas-dynamic upper frequency limit. Therefore, it is essential to better understand the process of burned gas backflow for minimizing the purge layer thickness. The flow field of the semi-valveless PDC was visualized to illustrate the movement of burned gas. A combustor of length of 95 mm with a 10-mm-square cross section was used. Supercritical ethylene and oxygen gas were used as fuel and oxidizer, respectively, and the operation frequency was 604 Hz. The unsteady refilling process of the detonable mixture was modeled by an isentropic flow. In addition, the detailed burned gas blowdown process with deflagration-to-detonation transition (DDT) and the backflow were captured. It was shown that the retonation wave generated by the DDT process was the primary trigger of the burned gas backflow. When the duration required for the DDT process was sufficiently shorter than that of the burned gas blowdown process, it was found the latter could be reproduced with approximately 90% accuracy by one-dimensional numerical analysis without the DDT process.

Validation of Pulse-Detonation Operation in Low-Ambient-Pressure Environment

A pulse-detonation thruster can generate a high-repeatability small impulse at a high operating frequency. To operate a pulse-detonation cycle in a vacuum environment without a purging material, a liquid-purge method proposed by Matsuoka et al. (“Development of a Liquid-Purge Method for High-Frequency Operation of Pulse Detonation Combustor,” Combustion Science and Technology, Vol. 187, No. 5, 2015, pp. 747–764) and throat at the exit of the combustor were introduced. In the demonstration experiment, gaseous ethylene–liquid nitrous oxide, as detonable mixture, and a throat having an inner diameter of 3.6 mm (blockage ) were used. The measured cyclic flame-propagation speeds were and of the estimated Chapman–Jouguet detonation speed. Consequently, a 50 Hz pulse-detonation operation without a purging material in the ambient-pressure range of 0.035–1.5 kPa was confirmed. A quasi-steady model, in which gases in the combustor are in the stationary state, was newly developed to investigate the operating characteristic of the pulse-detonation thruster. The experimental pressure history in the combustor during the burned-gas blowdown process was in good agreement with that of the model. Moreover, using the model, the thrust performance of the pulse-detonation thruster with a converging–diverging nozzle was investigated. It was found that the estimated specific impulse was comparable with that of the theoretical steady-state rocket engine.

A new integrated approach to study the thermal and mechanical response of vessels subject to a safe blowdown process

The problems related to the blowdown of pressure vessels containing mixtures of hydrocarbons are well known amongst industries involved in plant design and hydrocarbons extraction. In this paper a new integrate approach to study the rapid two-phase depressurization (blowdown) of a vessel containing a mixture of hydrocarbons is presented. The method presented is based on a new mathematical model developed by some of the authors for the thermo-fluid dynamic characterization of the process (VBsim) and the finite element analysis for the mechanical simulations. Indeed, the pressure and thermal stress levels to which the vessel is exposed during the blowdown can present a number of consequences, such as cracks in the walls that have to be predicted by an accurate simulation of the blowdown process. In addition, from the economic point of view it is important to properly simulate the two-phase vessel blowdown to ensure the selection of the most cost-effective materials to conduct this operation in safe conditions. To demonstrate the effectiveness of the present approach, a vessel blowdown case from literature has been simulated and the most critical points in terms of thermal and mechanical stresses of the vessel wall have been identified. In addition, the FEM model build up can be used also for a complete Design of Experiments (DOE) analysis.

Combustion effects of a staged transverse jet and pulsed detonation in supersonic crossflow

The combustion effects of a H2/O2 pulsed detonation (PD) staged downstream of a primary transverse H2 jet in supersonic crossflow (JICF) was investigated. A Mach 2.35 crossflow representative of Mach 7 flight combustor entry conditions (T∞=1330K, P∞=40kPa) was considered. The jet-to-crossflow momentum flux ratio (Jj) of the primary jet was varied between 0.5 and 5.0 to span different stabilization modes. The PD provides a short-duration, high temperature and momentum, radical-rich plume of gas to the wake of the primary transverse jet. The temporal evolution of the interaction between the two plumes was studied using high-speed schlieren and OH* chemiluminescence imaging. Phase-locked OH planar laser-induced fluorescence imaging was used to identify the instantaneous reaction zone along the center-plane at various times of the blowdown process. It was found that the interaction of the two plumes promotes earlier ignition and release of heat. The presence of a high momentum flux ratio transverse jet increases the effective blowdown period (EBP) over which OH* is exhausted; thus increasing the duration of the effects of the PD on the JICF. Lastly, the penetration of the reacting layer into the crossflow was observed to increase with the staged PD present as compared to cases without it.

Characterization of Produced and Residual Oils in the CO2 Flooding Process

In immiscible CO2 flooding processes, the injected CO2 extracts light and intermediate components from reservoir hydrocarbons, changing the properties of both the produced and residual oils. CO2 injection also increases asphaltene precipitation, which further causes adverse effects on the oil effective permeability, operational facilities, and the oil recovery. In this study, six CO2 flooding followed by blowdown processes are carried out in the laboratory under four CO2 injection pressures and two temperatures, and the properties of produced and residual oils are further characterized. It is found that uneven residual oil distribution occurred due to the coupled effects of viscous fingering and oil properties changes during CO2 flooding process. Characterization of the produced oil shows that both the produced oil density and viscosity decrease when CO2 injection pressure increases. The asphaltenes content of the oil produced after CO2 breakthrough is found to be relatively lower than that of the oil sam...

Behaviors of passive safety systems under a Feed Water Line Break LOCA on a Generation III+ Boiling Water Reactor

A postulated Large Break Loss-Of-Coolant-Accident (LB LOCA) on a generic Generation III+ Boiling Water Reactor (BWR) equipped with passive safety systems has been analyzed by conducting integral tests at a scale-down test facility, named Purdue University Multi-Dimensional Integral Test Assembly (PUMA). The integral tests simulate the hypothetical Feed Water Line Break (FWLB) accident caused by a guillotine rupture of the Feed Water Line (FWL) attached to the reactor vessel. This research is motivated to evaluate the behaviors of passive safety systems and to provide experimental data for the Validation and Verification (V&V) of related system codes. The experiment simulates the LOCA transient after the reactor vessel depressurizes to 1 MPa (150 psi) from normal operating pressure. The early high-pressure blowdown process of LOCA transient is simulated by the system code. The plant system conditions at 1.0 MPa calculated by the system code are interpreted as the initial conditions for the integral test with appropriate scaling. The normal FWLB integral test is also repeated with the partial failure of the PCCS to evaluate the safety margin. Experimental data indicates that this LB LOCA is successfully mitigated by the functioning of Emergency Core Cooling System (ECCS) and Passive Containment Cooling system (PCCS), with no occurrence of core uncover or containment overpressure.

Advanced Flow Control for Supersonic Blowdown Wind Tunnel Using Extended Kalman Filter

Supersonic blowdown wind tunnels provide controlled test environments for aerodynamic research on scaled models. During the experiments, the stagnation pressure in the test section is required to remain constant. Due to nonlinearity and distributed characteristics of the controlled system, a robust controller with effective flow control algorithms is required for this type of wind tunnels. In this paper, an extended Kalman filter (EKF) based flow control strategy is proposed and implemented. The control strategy is designed based on state estimation of the blowdown process under the EKF structure. One of the distinctive advantages of the proposed approach is its adaptability to a wide range of operating conditions for blowdown wind tunnels. Furthermore, it provides a systematic approach to tune the control parameters to ensure the stability of the controlled air flow. Experiments with different initial conditions and control targets have been conducted to test the applicability and performance of the designed controller. The results demonstrate that the controller and its strategies can effectively control the stagnation pressure in the test section and maintain the target pressure during the stable stage of the blowdown process.